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Utilizing intermolecular hydrogen‐bonding interactions stands for an effective approach in advancing the efficiency and stability of small‐molecule acceptors (SMAs) for polymer solar cells. Herein, we synthesized three SMAs (Qo1, Qo2, and Qo3) using indeno[1,2‐b]quinoxalin‐11‐one (Qox) as the electron‐deficient group, with the incorporation of a methylation strategy. Through crystallographic analysis, it is observed that two Qox‐based methylated acceptors (Qo2 and Qo3) exhibit multiple hydrogen bond‐assisted 3D network transport structures, in contrast to the 2D transport structure observed in gem‐dichlorinated counterpart (Qo4). Notably, Qo2 exhibits multiple and stronger hydrogen‐bonding interactions compared with Qo3. Consequently, PM6 : Qo2 device realizes the highest power conversion efficiency (PCE) of 18.4 %, surpassing the efficiencies of devices based on Qo1 (15.8 %), Qo3 (16.7 %), and Qo4 (2.4 %). This remarkable PCE in PM6 : Qo2 device can be primarily ascribed to the enhanced donor‐acceptor miscibility, more favorable medium structure, and more efficient charge transfer and collection behavior. Moreover, the PM6 : Qo2 device demonstrates exceptional thermal stability, retaining 82.8 % of its initial PCE after undergoing annealing at 65 °C for 250 hours. Our research showcases that precise methylation, particularly targeting the formation of intermolecular hydrogen‐bonding interactions to tune crystal packing patterns, represents a promising strategy in the molecular design of efficient and stable SMAs. [ABSTRACT FROM AUTHOR]

Nowadays, it is still a great challenge to obtain high‐performance green‐solvent‐processed organic solar cells (OSCs). In this study, a ternary blend strategy (one donor and two acceptors, 1D/2A) is developed to solve the difficulty of film morphology modulation during the fabrication of high‐performance green‐solvent‐processed OSCs. A typical high‐performance halogenated‐solvent processable binary system D18:BTP‐eC9‐4F is selected as the host, its green‐solvents‐processed devices show an inferior power conversion efficiency (PCE) of ≈16%. SM16 with two 3D shape persistent end groups is selected as the third component due to its high fluorescence quantum yield, reduced intermolecular interaction, good solubility, and moderate crystallinity. As a result, the ternary devices display bicontinuous interpenetrating networks, reduced energy loss, and suppressed charge carrier recombination losses. Hence, an excellent PCE of 18.20% is achieved for the D18:BTP‐eC9‐4F:SM16 ternary devices, which is much higher than D18:BTP‐eC9‐4F‐based binary ones and also one of the highest PCEs for the green‐solvents‐processed OSCs. Besides, this strategy also demonstrates a good universality for other binary systems and becomes an effective pathway for the development of green‐solvent processable high‐performance OSCs. [ABSTRACT FROM AUTHOR]

The research on perylene diimide (PDI) aggregates effectively promotes their applications in organic photovoltaic solar cells and fluorescent sensors. In this paper, a PDI fabricated with three peripheral PDI units (N, N'-bis(6-undecyl) perylene-3,4,9,10-bis(dicarboximide)) is investigated. The trimer shows different absorption and fluorescence properties due to hydrophobicity when dissolved in the mixed solvent of tetrahydrofuran (THF) and water. Through comprehensive analysis of the fluorescence lifetime and transient absorption spectroscopic results, we concluded that the trimer underwent different excited state kinetic pathways with different concentrations of water in THF. When dissolved in pure THF solvent, both the intramolecular charge-transfer and excimer states are formed. When the water concentration increases from 0 to 50% (v/v), the formation time of the excimer state and its structural relaxation time are prolonged, illustrating the arising of the intermolecular excimer state. It is interesting to determine that the probability of the intramolecular charge-transfer pathway will first decrease and then increase as the speed of intermolecular excimer formation slows down. The two inflection points appear when the water concentration is above 10% and 40%. The results not only highlight the importance of hydrophobicity on the aggregate properties of PDI multimers but also guide the further design of PDI-based organic photovoltaic solar cells. [ABSTRACT FROM AUTHOR]